Are we suppose
to include the picture of our final work in the portfolio as well? Because my art teacher told me it's required but some students from other ib schools have not included it as it should include only the process.

I've had two different art teachers in my school tell me two different things. Past students told me it doesn't harm you either way but seeing as you're presenting the final work in your exhibition I'd play it safe and only include WIP in your portfolio